Method 50 patients with rotator cuff tears who had undergone arthroscopic rotator cuff repairs were enrolled in this study. Rotator cuff tears were diagnosed by preoperative magnetic resonance imaging, and the size of the rotator cuff was confirmed at the time of arthroscopic operation. Indication for surgery was a symptomatic full-thickness rotator cuff tear or a partial thickness rotator cuff tear of more than 50% thickness in case of failed conservative therapy. Twenty-five patients were randomly allocated to group 1 and received both ISB with 8mL of ropivacaine with 100 μg (1ml) of dexmedetomidine . The other 25 patients were allocated to group 2 and received ISB with 8mL of ropivacaine with 1ml of normal saline.